/Engine/Source/Runtime/MeshDescription/Public/MeshDescription.h
Adds a new polygon to the mesh with the given ID. This will also make any missing edges, and all constituent triangles.
void CreatePolygonWithID ( const [FPolygonID](API\Runtime\MeshDescription\FPolygonID) PolygonID, const [FPolygonGroupID](API\Runtime\MeshDescription\FPolygonGroupID) PolygonGroupID, [TArrayView](API\Runtime\Core\Containers\TArrayView)< const [FVertexInstanceID](API\Runtime\MeshDescription\FVertexInstanceID) > VertexInstanceIDs, [TArray](API\Runtime\Core\Containers\TArray)< [FEdgeID](API\Runtime\MeshDescription\FEdgeID) > * OutEdgeIDs )